1. Field of the Invention
The invention relates to a torque fluctuation absorbing apparatus having a structure for reducing misalignment of a torque limiter during assembling of the apparatus, and also relates to a method for assembling the torque fluctuation absorbing apparatus while reducing misalignment of the torque limiter when it is mounted in the apparatus.
2. Description of Related Art
A torque fluctuation absorbing apparatus is coupled to and between an engine crankshaft and an input shaft of a driven-side assembly (e.g., a transmission of a hybrid vehicle which houses a motor) so as to reduce engine torque fluctuations.
FIG. 8 and FIG. 9 show a known example of torque fluctuation absorbing apparatus. The torque fluctuation absorbing apparatus 1 includes a flywheel 10 coupled to a crankshaft 2 of an engine, a damper assembly 20 disposed in a torque transmission path between the flywheel 10 and a driven-side input shaft 3, and a torque limiter 30 disposed in a torque transmission path between the flywheel 10 and the damper assembly 20. The damper assembly 20 has a pair of drive plates 21, a driven plate 22, and spring dampers 24. The torque limiter 30 has a pair of linings 31 and a damper cover 32, and is adapted to slip when receiving a predetermined or larger amount of torque.
The pair of linings 31 are secured to both faces of an outer peripheral portion of one of the drive plates 21 (or a member fixed to the drive plate 21). The pair of linings 31 are sandwiched between the damper cover 32 and the flywheel 10. When a torque that is equal to or larger than a predetermined value is applied to the torque limiter 30, slippage occurs on surfaces of the linings 31 that are in contact with the damper cover 32 and the flywheel 10. The drive plates 21 and the driven plate 22 are rotatable relative to each other in a circumferential direction thereof. Also, small amounts of radial clearances are provided between a bush 23 disposed between the drive plate 21 and the driven plate 22, and the drive plates 21 and the driven plate 22, respectively, whereby the drive and driven plates 21, 22 rattle in the radial directions. In order to allow or accommodate rattling and assembling errors, a radial clearance d is provided between an outer periphery of the drive plate 21 (or a member secured thereto) and an inner periphery of the flywheel 10.
A procedure of assembling the known torque fluctuation absorbing apparatus 1 is as follows: (1) a hub 22a of the driven plate 22 of the damper assembly 20 and the crankshaft 2 are aligned with an engine assembly by using a jig 50, as shown in FIG. 9, (2) the damper cover 32 is bolted to the flywheel 10, and the damper cover 32 and the flywheel 10 sandwich the linings 31 secured to the drive plate 21 to thereby support the damper assembly 20, and (3) the engine assembly is assembled with a driven-side assembly, and these assemblies are thus fixed to each other.
The known apparatus, however, has following problems.
In the presence of the radial clearance between the drive plate and the driven plate as described above, the drive plate may be disposed ecccentrically within the range of the clearance with respect to the flywheel, even with the driven plate being properly aligned with the engine assembly by using the jig upon assembling of the torque fluctuation absorbing apparatus with the engine assembly. As a result, the linings of the torque limiter secured to the drive plate may be out of alignment with respect to the flywheel in the radial directions. If the torque limiter is assembled eccentrically with the engine assembly, the following and/or other problems may occur when the engine is rotated, after assembling of the engine assembly with the driven-side assembly, to an angular point where the radial clearance between the drive plate and the driven plate disappears. For example, 1) the rotation of the input shaft of the driven-side assembly may become unstable or fluctuating due to the eccentric arrangement of the drive and driven plates, and torsional stress may be applied to a bearing 60 that supports the input shaft of the driven-side assembly, resulting in a reduction in the service life of the bearing 60, 2) the service life of a bushing 61 (or a needle bearing) that is in sliding contact with the driven-side input shaft during rotation thereof may be shortened, and 3) the performance of an oil seal 62 that is in sliding contact with the driven-side input shaft may deteriorate.